10sec gtr's

[Whoneedstherapy]

i know there are a lot of gtr's running over the 500hp range, i dont know how much horsepower 305 kw@all4 wheels is, but ill find out soon

350kw is 469.3hp

305kw is 409hp

suffice to say your gtr should have just a tad over 500hp at the crank

It'll be great to see what times you can crack, i'll be running a similar setup when and if the bloody thing every gets here, except i'll have a little more displacement behind it. Would be good to see the difference in power curves and times.

[nicknick]

well i was told, not being an expert or anything, but when you dyno a 4 wheel drive car you loose about 50% of the power through the drive line, if thats true then i think is should be a little more then 500 if what i was told was correct

305kw + 50% = 450kw @ flywheel multiplied by 1.3 to convert to horsepower = 595hp

please correct me if im wrong, or if the percentage is deffernt for 4wheel drives,

i also heard it might be as much a 60% loss on the dyno.

[Whoneedstherapy]

well i was told, not being an expert or anything, but when you dyno a 4 wheel drive car you loose about 50% of the power through the drive line, if thats true then i think is should be a little more then 500 if what i was told was correct

305kw + 50% =  450kw @ flywheel  multiplied by 1.3 to convert to horsepower = 595hp

please correct me if im wrong, or if the percentage is deffernt for 4wheel drives,

i also heard it might be as much a 60% loss on the dyno.

i highly doubt you'd lose 50%-60% through the dyno, though i was kidding when i said just a tad, it should have a fair bit over 500hp

that said, as for R32 gtr's which when they have traction dont put any power to the front wheels, do they record a measurably loss when running with the atessa system on? has anyone actually done back to back runs, with and without atessa?

[Panda_ET]

i highly doubt you'd lose 50%-60% through the dyno, though i was kidding when i said just a tad, it should have a fair bit over 500hp

that said, as for R32 gtr's which when they have traction dont put any power to the front wheels, do they record a measurably loss when running with the atessa system on? has anyone actually done back to back runs, with and without atessa?

I read in some book somewhere about 4wd drivetrains can loose up to 40%(depending on the weight of the drivetrain components) of crank power thru drivetrain weight. Thats why things like carbon driveshafts exist.

well thats the way i look at it.

[Whoneedstherapy]

I read in some book somewhere about 4wd drivetrains can loose up to 40%(depending on the weight of the drivetrain components) of crank power thru drivetrain weight. Thats why things like carbon driveshafts exist.

well thats the way i look at it.

that loss would be because the engine would be driving the said components 100% of the time though, unlike gtr's which dont put power through the front wheels, and im assuming the front half of the drivetrain until there is a detected loss in traction. Therefore why would a 4wd like drivetrain loss be encountered if there was no loss in traction hence forth no power put through the front half of the drivetrain?

[MattyB]

you clocked it? is it aftermarket speedo or ?

[meshmesh]

I really think the drivetrain loss is irrelevant, because the power we want is at the wheels and this is where it "consistantly counts". I also think its more equal in measuring comparative result. Unlike at the fly/engine readings [insert sarcasm here] we need to be Einsteins' = fly divided by ~drivetrain loss % X hp to the square of ~0.00dg celsius... etc etc Who cares!!! just get it there please

[Corse]

The 60 foot time is indicative of a slipping clutch, and the trap speed is indicative of big power.

This is just a very unsorted car that happens to make alot of power. It has the potential.

50-60% drivetrain loss is quite far from the truth. realistically, 35% would be quite 'high'-ish. I have seen evidence that suggests the the 4WD system in GTR's only lose about 2% more than an equivelant RWD. Instead of the power being transmitted through the chunky rear driveshafts and diff, it goes through the transfer case and smaller front diff and lighter driveshafts, so it shouldent be losing much more power at all.

I think that you have quite a sexy car on your hands, and I beleive your car has the potential. don't take any skepticism too harshly as this IS an internet forum, and it's wise to beleive half of what you see and none of what you hear (or read, in this case).

As meshmesh said, I think drivetrain loss is irrelevant (unless youre calculating fuel, compressor flow or how long a peice of the drivetrain will last etc.) Its the amount of power that gets to the ground that counts.

[nicknick]

yeah you know what, who really cares what the drivtrain power loss is, running it at the quatre and gettting that all important paper which states your E.T time is most important, i heard tehre is a dyno run in sydney somwhere on monday, have to find out where, and go down and see what other gtr's pull on the dyno

[Sydneykid]

Hi guys, this drive train loss is pretty simple high school physics really. Newton's theory says that energy can neither be gained nor lost, it can however be transformed into other types of energy, ie torque into heat via friction etc.

Each car transforms a different amount of torque, a rear wheel drive car will transform more than a front wheel drive car because the front wheel drive car has no tailshaft universals and right angle drive to the differential. Obviously a four wheel drive transforms even more, it has 3 diffs, 2 sets of drive shafts etc.

Then there is the small gearbox versus the large gearbox, ditto diff. So a Commondoor with a huge gearbox and diff, big tailshaft and universals, large wheel bearings etc etc wil obviously transform more torque into heat.

Some results we have seen;

An R32 GTST standard 160 kw makes 110 rwkw

An R33 GTST standard 180 kw makes 125 rwkw

An R32 GTR standard 225 kw (the accepted 206 +) makes 165 rwkw and 150 4wkw. Losses of 60 kw and 75 kw respectively. Calculating the percentage that would be 29% and 33% respectively.

I have previously installed, into an R32 GTR, an RB30/25 that made 360 kw on the engine dyno. On the rollers it made 295 rwkw and 278 4 wkw. Losses of 65 kw and 82 kw, pretty close to the previous RB26 losses.

If I had experienced the percentage loss of 29% it would have only made 255 rwkw and 241 4wkw at 33%.

I could give you at least 10 other examples of engines we have run on the engine dyno and then on the rollers, and they would show the same result. Sure there is a little more losses but nowhere near what you would expect using the percentage theory.

Think about it in reverse..........

What if I put in a straight cut gearbox (substantially less friction), the car will show more power at the rear wheels, but it will have the same at the engine. How does the fixed percentage method allow for that?

Hope that helps

[nicknick]

man you just F*cked my whole night up, i have no idea what you just wrote in your message.

[Sydneykid]

Hi nick, try this.......

I have a car with 200 rwkw that has 250 kw at the engine.

So it transforms 50 kw (250 - 200) into heat.

I whack a great big turbo on it and do a whole pile of other stuff.

Now it puts out twice as much power = 400 rwkw.

How much power does it transform into heat?

Using the % method you would say it losses 25% (50 / 200) and when you double the power at the wheels, that would be 100 kw. If it did, you could cook eggs on the gearbox case. Think about how much heat a 1 kw radiator puts out, and multiply it by 100.

I reckon it still transforms 50 kw (give or take a bit) the same as it did when standard.

Hope that is easier to understand.

[Sumo]

makes sense,

Thats what I was thinking ages ago e.g. no matter how big your donk is it will still only have X amount a kw lost to the drivetrain, because everything else has stayed the same. yet you hear of people quoting loss in percentages - which make work for cars with the stock output (what the loss percentage has been calculated around)

Sumo

[Sydneykid]

Hi Sumo, in my opinion the reason a lot of people use the percentage loss method is that it makes their engine sound more powerful than if they used the fixed loss method. I see this all the time from car owners, engine builders and, most of all, tuners.

It is easy to see why.................

200 rwkw engine + losses 50 kw (25%) = 250 kw at the engine

400 rwkw + 25% = 500 kw at the engine

Sounds much more impressive than.............

200 rwkw engine + losses 50 kw = 250 kw at the engine

400 rwkw + 50 kw losses = 450 kw at the engine

Which engine power output would you much rather brag about 450 kw or 500 kw?

Now, I should point out that I have no doubt that the loss is not perfectly constant. The load on gears with extra torque transmission, in particular, increases the component heat. That comes from extra losses, but not anywhere near double. I have measured the gearbox and diff temperatures on the dyno at 2 power levels (0.8 bar & 1.5 bar) and the pyro shows very small increases. So I would accept an argument that said the 50 kw, in my 200 rwkw, example may well be say 55 kw when power is increased to 400 rwkw. But that's about it, there is no way it is 100 kw.

Hope that clarifies.

[meshmesh]

The main use of Engine power would be for motor-racing sports where they may be limited to enhine hp. How they get it to the ground & minimise loss, is another question??

Sydneykid,

Not sure if this is the case or not but I'll assume so...

if Touring cars & some motorsports categories are restricted to "Engine power eg: 650hp" then it's to their advantage to minimise loss of power to the wheels..

You're talking about heat & Newtons theory, how can you minimise loss from fly to wheels?

PS: Thanks for the PM, ordered the GT2530's, might stick with stock dumps, some think there's no real benefit. :confused:

[nicknick]

thanks Sydneykid for the info, but wouldnt you loose more then 50-60kw throguh the drive train if your producing 400+kw at flywheel, my mate hsa a evo3 and produces 150kw @4wheels, yet he has a 300kw motor

[vspecv]

thanks Sydneykid  for the info, but wouldnt you loose more then 50-60kw throguh the drive train if your producing 400+kw at flywheel, my mate hsa a evo3 and produces 150kw @4wheels, yet he has a 300kw motor

good luck nicknick on the 10 your hoping for, but doubt it will ever happen.

even at ur estimated 370kw, its still not enough and with that laggy t78 gettin off the line is gunna be your biggest problem, ditch the turbo and u may have a shot.

[nicknick]

dean i hope thats you, man even with this laggy turbo ive done a 8000rpm launch, and seriously there wasnt much deffernce in take off to a r32 gtr with low mounted turbos, im having C&V performance tune it on C16 next week for the runs and installing a 50shot of nos for take off. hopefull ill have a good time, i mean even if i dont hit 10s at the creek 11's on street tyred will still be ok as a weapon on the road. running 22psi and tuned on C16 should help a little :flamed: :Bang:

[vspecv]

yep its me.

11s is still damn fast, but i think ur going to see the difference between a street tyred 11 is a world away from a 10.

ur gunna need some nittos aswell if u really want a shot at 10s.

try a 150hp shot, some nittos and drive it like u stole it and u may just drop into the 10s

[Sydneykid]

Hi meshmesh, you asked "how can you minimise loss from fly to wheels"

Let me emphasise that there is no LOSS, the energy is CONVERTED into something else. In the case of a car it is kinetic energy CONVERTED into heat. To minimise this, you use things like straight cut gears instead of helical cut ones. You use lighter grade oil in the gearbox and diff. You use looser and or more efficient bearings in the gearbox, diff and wheel bearings. Tight bearings create heat. You keep the tailshaft universals and drive shaft CV's straight, if they have angles they soak up power and turn it into heat. etc etc

Hi nicknick, I have had a RB25 on the engine dyno and then put it in the car, it showed 60 kw in transformation to heat. I have also had an RB31DET on the engine dyno and then put it in the car, it showed 62 kw in transformation to heat. If you take the standard power of an RB20, RB25 and RB26 and run it up on our dyno they show 50 to 60 rwkw down on the quoted power every time. We have done this at least 20 times with different models of Skylines

Think about your mate with 300 kw and only 150 rwkw? Where does the heat go? Remember that's 150 kw, it's the same as 150 X 1 kw radiators, you know how much heat a 1 kw radiator puts out. Man you could fry eggs on the gearbox case and cook the bacon to match on the diff case. A GTR only transforms around 85 kw from engine kw to 4wkw, there is no way an Evo is gunna get anywhere near that. Your mate hasn't got a 300 kw engine, more like a 230 kw engine if all it gets is 150 4wkw.

Hope that helps clarify.

PS, we ALWAYS find power from fitting split dumps, plus a bit of earlier boosting. I am not a fan of the short HKS style of split dump though, they are not separated for long enough. We always use at least 400 mm before we plumb the wastegate outlet back into the turbine outlet.